The present invention concerns muntin bars used for separating window panes of large size into smaller size panes to enhance the appearance of a window.
Windows constructed from multiple glass panes utilized xe2x80x9cmuntinsxe2x80x9d or xe2x80x9cmuntin barsxe2x80x9d to secure the edges of the individual glass panes within the window sash. In many windows, muntins formed distinctive grid patterns that are associated with architectural styles of buildings containing the windows.
Modern windows formed by insulating glass units utilize single glass lites separated by an insulating dead air space. Where a particular architectural xe2x80x9clookxe2x80x9d is desired, a grid of muntin bars is fixed in the dead air space between the glass lites to simulate a multi-pane window. Typical muntin bars for insulating glass units are formed from decoratively coated interfitted metal tubes. The grids are anchored to the insulating glass unit periphery.
Constructing muntin bar grids for insulating glass units has been a labor intensive process. As a consequence, manufacturing such units, and thus windows formed by the units, has been costly and inefficient. Some efforts to mechanize the manufacture of muntin grids have been made. Commonly owned U.S. Pat. No. 6,173,484 entitled xe2x80x9cSystem for Fabricating Muntin Bars from Sheet Materialxe2x80x9d which issued Jan. 16, 2001 to McGlinchy et al. is an example of a system for automated fabrication of muntin bars. The subject matter of this patent is incorporated herein by reference. Commonly owned pending U.S. patent application Ser. No. 09/525,349 entitled xe2x80x9cSystem for Fabricating Contour Muntin Bars from Sheet Materialxe2x80x9d is a second patent application to McGlinchy et al concerning automated fabrication of so-called contour muntin bars and the subject matter of this application is incorporated herein by reference.
The muntin bar stock is produced by roll forming decoratively coated sheet material such as aluminum or steel, in a known manner. Various sizes of the sheet material are used to form different size muntin bar stock. The roll forming machine has a series of rolls configured to form sheet material into elongated tubular muntin bar stock. A window manufacturer purchases the muntin bar stock size(s) needed to produce insulating glass units. Apparatus disclosed in the aforementioned patent application also cuts the stock into lengths that are notched in appropriate locations for assembly into grids for incorporation into the insulating glass units.
The residential window and door industry has witnessed an increased demand for internal decorative muntin bars contained in insulated glass units (IGUs) of their windows. This market demand for muntin bars has increased due to popular xe2x80x9ccolonial lookxe2x80x9d trends in the market. Also contributing to the demand are new construction and residential building codes requiring a common facade in local neighborhoods. With people also desiring differentiation and designer choices in their windows, a demand for so-called xe2x80x9ctwo tonexe2x80x9d muntin bars is on the rise. The two tone muntin bar assembly presents one appearance from the outside and a second appearance from inside the window.
Two-tone muntin bars are offered today in many color combinations for both rectangular and contour style muntin bars. A two-tone muntin bar demands a premium price in the market place. One reason for the increased price of two tone muntin bars is the fact that automated manufacturing of two tone muntin bars using controlled notching, roll forming and severing has not occurred.
The most common method practiced at the present time for manufacturing two tone muntin grids starts with a long roll formed bar that is often shipped to a secondary supplier that paints or laminates the bar with a solid color tone or wood pattern on one side and a second color or wood pattern on the opposite side. Use of multiple steps performed by multiple suppliers results in significant additional cost to the product. More elaborate bars have simulated wood grains that are used to match up with the wood trim in or surrounding the window sash. All of the current methods require cutting specified length segments from a two tone bar. This bar is then mitered and/or punched to complete fabrication of the muntin bar. The current methods require post painting and/or lamination of the formed muntin bar which is time consuming, costly and constrained throughput in a production environment. The current process also leads to a build up of material inventory to give the suppliers adequate lead time for performing these post roll forming procedures.
The present invention concerns an automated method and apparatus for producing notched muntin bars from a supply of sheet material having first and second finishes. In accordance with one process muntin bars having first and second finishes are provided that have one appearance when viewed from outside the window and a second appearance when viewed from inside the window.
In an exemplary embodiment of the invention a supply of thin sheet material that has been treated to define first and second finishes on one side of the sheet material is provided. Sections of the material having the first finish and sections of the material having the second finish are removed from the sheet material. The sheet material is then formed into an elongated tubular muntin bar stock. The muntin bar stock has a first side having the first finish and a second side having the second finish. The muntin bar stock has notches in the first side that correspond to the removed sections of material having the first finish. The formed muntin bar stock has notches in its second side that correspond to the removed sections of material having the second finish. The muntin bar stock is severed at predetermined locations to form individual notched muntin bars. The notches in the individual muntin bars are located along the length of the muntin bars to allow the individual muntin bars to be combined to form a muntin bar grid having a first side with the first finish and a second side with the second finish.
One aspect of the invention is used to make a first set of muntin bars that will be assembled in a first orientation. Each of the muntin bars in the first set of muntin bars includes notches only in the side having the first finish. Each muntin bar in a second set of muntin bars that will be assembled in a second orientation includes notches only in the side having the second finish. By notching the muntin bars that will be assembled in the first orientation only on one side and notching the muntin bars that will be assembled in the second orientation on the opposite side, a muntin bar grid having first and second finishes on opposing sides is easily assembled.
An apparatus for making notched muntin bars having sides with first and second finishes includes a ribbon stock support or uncoiler, a notching device, a roll forming machine and a severing device. The uncoiler supplies the ribbon stock having one surface with first and second finishes. The notching device receives the ribbon stock from the supply of ribbon stock. The notching device has a punch that is movable between a first position where the punch is engageable with ribbon stock having the first finish and a second position where the punch is engageable with ribbon stock having the second finish. The roll forming machine receives ribbon stock from the notching device to form hollow muntin bar stock that has a first side with the first finish and a second side with the second finish. The formed muntin bar stock has notches in one side that correspond to removed sections of material having the first finish and notches in the second side that correspond to removed sections of material having the second finish. The severing device severs the formed muntin bar stock to form individual notched muntin bars having sides with first and second finishes.
In the exemplary embodiment, the notching device includes a pneumatic cylinder that moves the punch between the first and second positions. A control is coupled to the pneumatic cylinder which causes the cylinder to move the punch to the first position when stock corresponding to a muntin bar that will be assembled in a muntin bar grid in a first orientation is being punched. The control causes the cylinder to move the punch to the second position when the stock corresponding to a muntin bar to be assembled in a muntin bar grid in a second orientation is being punched.
These and other objects, advantages and features of the invention will become better understood from a review of the exemplary embodiment of the invention which is described in conjunction with the accompanying drawings.